Rohde & Schwarz SMB100A - Page 158

R&S SMB Troubleshooting
1407.0806.82 3.19 E-6
Fault Test Action if test fails
Amplitude
Modulation
Faulty
The AM is specified only up to the Peak
Envelope Power (PEP) noted in the
datasheet. The PEP value of an AM signal
with depth m at setting level P is
P
P
EP
= Level + 20 log
1
0
(1+ m/100)
So at m = 100 % the PEP is 6.02 dB higher
than the setting level shown in the display.
The AM performance has to match the values
given in the datasheet. Measure with a true
demodulating receiver, i.e. a R&S FSMR or
R&S FSL/ FSP/ FSU/ FSQ spectrum analyzer
equipped with option R&S K7
Most probably the RF Board is
defective. Check the RF Board
being supplied correct (see
page 3.24).
Frequency/
Phase
Modulation
Faulty
FM and PhiM Modulation are generated in the
DDS synthesizer reference signal on the RF
Board. Run Internal Adjustments to ensure
the VCOs generating the RF signal working in
their optimum.
The FM performance has to match the values
given in the datasheet. Measure with a true
demodulating receiver, i.e. a R&S FSMR or
R&S FSL/ FSP/ FSU/ FSQ spectrum analyzer
equipped with option R&S-K7
Most probably the RF Board is
defective. Check the RF Board
being supplied correct (see
page 3.24).
Pulse
Generator/
Pulse Modulator
Faulty
The pulse generator is implemented fully
digital in the RF Board FPGA. The pulse
signals are fed exclusive on the RF Board to
the pulse modulator switch. All external
pulse-BNC connectors are fitted on the RF
Board as well.
Most probably the RF Board is
defective. Check the RF Board
being supplied correct (see
page 3.24).
Signal Valid This signal is driven from the RF Board FPGA
and the Signal Valid BNC connector is directly
fitted onto the RF Board as well.
Most probably the RF Board is
defective. Check the RF Board
being supplied correct (see
page 3.24).
Faulty Remote
interface
IEEE488, USB
or LAN
All remote interfaces including the interface
connectors are fitted directly on the Basis
Board.
Most probably the Basis Board is
defective. Check the Basis Board
being supplied correct (see page
3.21).
External Stereo
input Faulty
(only applies if
option
R&S SMB-B5
Stereo/RDS
Coder is
installed)
Measure the input resistance of the STEREO
L, R inputs on the rear panel with a
multimeter. The input resistance should be
600 K ± 20 % or 200 kK ± 20 % dependent on
the setting in the Stereo menu
Measure the input resistance of the STEREO
S/P DIF input on the rear panel with a
multimeter. The input resistance should be
75 K ± 20 %.
Check the connection of STEREO L,
R, S/P DIF cables to the Stereo
Coder module (0).
If connected correct most probably
the Stereo Coder module is
defective. Check the Stereo Coder
being supplied correct (see page
3.32).